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【Java】实现牛顿插值法

作者:郑岸以 / 发布于2014/10/8/ 527


	import java.util.Scanner;
	
	
	public class Newton_interpolation {
	 /*拷贝向量*/
	 private static void copy_vector(double from[],double to[]){
	 int k=from.length;
	 int k2=to.length;
	 if(k!=k2){
	 System.out.println("the two vector's length is not equal!");
	 System.exit(0);
	 }
	 for(int i=0;i<k;i++){
	 to[i]=from[i];
	 }
	
	 }
	
	 /*牛顿插值法*/
	 private static double[] Newton_inter_method(double[] X,double[] Y,double X0[]){
	 int m=X.length;
	 int n=X0.length;
	 double[] Y0=new double[n];
	 double[] cp_Y=new double[m];
	 for(int i1=0;i1<n;i1++){//遍历X0
	 double t=0;
	 int j=0;
	 copy_vector(Y, cp_Y);
	 int kk=j;
	 /*求各级均差*/
	 while(kk<m-1){
	 kk=kk+1;
	 for(int i2=kk;i2<m;i2++){
	 cp_Y[i2]=(cp_Y[i2]-cp_Y[kk-1])/(X[i2]-X[kk-1]);
	 }
	 }
	 /*求插值结果*/
	 double temp=cp_Y[0];
	 for(int i=1;i<=m-1;i++){
	 double u=1;
	 int jj=0;
	 while(jj<i){
	 u*=(X0[i1]-X[jj]);
	 jj++;
	 }
	 temp+=cp_Y[i]*u;
	 }
	
	 Y0[i1]=temp;
	 }
	
	 return Y0;
	 }
	
	
	 public static void main(String[] args) {
	 /*输入插值点横纵坐标*/
	 System.out.println("Input number of interpolation point:");
	 Scanner scan=new Scanner(System.in);
	 int m=scan.nextInt();
	 System.out.println("Input number of test point:");
	 int n=scan.nextInt();
	 double X[]=new double[m];
	 double Y[]=new double[m];
	 double X0[]=new double[n];
	 System.out.println("Input the elements of X:");//已知插值点
	 for(int i=0;i<m;i++){
	 X[i]=scan.nextDouble();
	 }
	
	 System.out.println("Input the elements of Y:");//已知插值点的函数值
	 for(int i=0;i<m;i++){
	 Y[i]=scan.nextDouble();
	 }
	
	 System.out.println("Input the elements of X0:");//需要求的插值点的横坐标标值
	 for(int i=0;i<n;i++){
	 X0[i]=scan.nextDouble();
	 }
	
	
	
	 }
	
	}

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　牛顿插值法　

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